1. Field of the Invention
This invention relates to sealed bearing rotary cone rock bits that utilize belleville seals.
More particularly, this invention relates to sealed bearing rotary cone rock bits that utilize belleville seals between a journal and a cone, the seal being metallurgically bonded and hermetically sealed between the static portion of the seal and its adjacent journal.
2. Description of the Prior Art
There are many patents relating to the use of belleville seals in rotary cone rock bits, most of which are expired.
An early Hughes patent, U.S. Pat. No. 3,075,781, describes a belleville seal disposed between a bearing spindle and a rotary cutter cone mounted to the spindle. A multiplicity of roller bearings are disposed between the rotary cone and the bearing spindle. The belleville seal is designed to "float" between the cone and bearing spindle. The seal face on the inner diameter of the belleville is positioned at the intersection of the spindle and leg backface and the opposite seal face of the outer diameter of the belleville is positioned against the cone backface--both seal faces are dynamic since both slide against their respective sealing surfaces. Experience has shown, however, that it is undesirable to have two dynamic sealing surfaces disposed between fixed and rotating parts.
U.S. Pat. No. 3,489,421, assigned to the same assignee as the present invention, describes a seal for use between relatively rotatable parts. This patent describes an improvement to belleville seals for use in rock bits. The seal consists of an annular metallic retaining ring having a resilient element bonded around one edge portion of the resilient belleville seal element. The retaining ring lies about and has an annular portion interferingly fitted in sealing contact on one of the relatively rotatable parts. The resilient element, in a relaxed position, has a relatively free annular edge portion with a wiping face disposed transversely of the axis of rotation and in sliding contact with one of the opposed surfaces. The metallic retaining ring is spot welded intermittently around the joint between the retaining ring and the journal.
The invention teaches either intermittent spot welds around the metal ring fitted to the journal or the use of a punch to distort one portion of the metallic retaining ring into the journal onto which the ring is connected. Obviously, the reason the belleville seal is spot welded is to prevent its rotation during operation of the bit in the borehole.
A further refinement of the belleville seal art resulted in U.S. Pat. No. 3,680,873, also assigned to the same assignee as the present invention. The seal includes an inner annular ring, preferably metallic, and an outer annular element of yieldable seal material. The inner resilient ring has a weakened breakpoint which will remain unbroken during the bonding of the annular yieldable rubberlike material to the ring. The ring is separable at the breakpoint when forced over an abutment on one of the relatively rotatable parts. The ring and yieldable material are returned or "spring back" to approximately their original diameters after passing the ridged abutment. The yieldable material is subjected to pressure deformation to tightly secure the resilient ring radially inwardly about the relatively rotatable part and axially outwardly against the abutment. The patent addresses the problem of securing the inner diameter static portion of the belleville seal against a rock bit leg backface to prevent the static portion or inner annular portion of the belleville seal from rotating. The present practice is to spot weld the inner metallic ring of the belleville seal to secure the broken ends of the ring and to prevent rotation of the ring during operation of the rock bit.
The present invention incorporates a design encompassing less machining operations as will become evident from the text of this disclosure. In the present invention, the inner metallic ring of the belleville seal is placed over the bearing journal with a slight interference fit. The inner metallic ring is then welded around its circumferential interface between the journal and the bearing ring. The necessity to mechanically lock an inner split ring over an abutment is therefore obviated. A high-energy beam welding process, such as continuous laser or pulsed laser or electron beam, is preferred because a 360.degree. weld on a typical journal can be completed in a few seconds. The beam is focused to a very small cross-sectional area at the intersection of the inner metallic ring of the belleville seal and the leg journal. The combination of the localized high-energy input and short welding time results in a weld that hermetically seals the static side of the belleville seal and does not degrade the elastomer material encapsulating the belleville spring or the metallic members.